Details

Autor(en) / Beteiligte

• Kampf, Anthony R
• Cooper, Mark A
• Celestian, Aaron J
• Ma, Chi
• Marty, Joe

Titel

Relianceite-(K), a new phosphate-oxalate mineral related to davidbrownite-(NH4) from the Rowley Mine, Arizona, USA

Ist Teil von

• Mineralogical magazine, 2022-08, Vol.86 (4), p.539-547

Ort / Verlag

London: Cambridge University Press on behalf of the Mineralogical Society of the UK and Ireland

Erscheinungsjahr

2022

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Relianceite-(K), K4Mg(V4+O)2(C2O4)(PO3OH)4(H2O)10, is a new mineral species from the Rowley Mine, Maricopa County, Arizona, USA. It occurs in an unusual bat-guano-related, post-mining assemblage of phases. Other secondary minerals associated with relianceite-(K) are antipinite, dendoraite-(NH4), fluorite, mimetite, mottramite, rowleyite, salammoniac, struvite, vanadinite, willemite, wulfenite and at least one other new mineral. Crystals of relianceite-(K) are sky blue prisms up to ∼0.1 mm in length. The streak is very pale blue and luster is vitreous, Mohs hardness is 2 1/2, tenacity is brittle and fracture is splintery. The calculated density is 2.111 g·cm-3. Relianceite-(K) is optically biaxial (+) with α = 1.528(2), β = 1.529(2), γ = 1.562(2) (white light); 2Vmeas = 22(1)°; orientation Z = b; pleochroism: X = colorless, Y = pale blue, Z = pale blue; X < Y ≈Z. Electron microprobe analysis gave the empirical formula [K2.21(NH4)1.79]Σ4.00 Mg0.96(V4+0.95O)2(C2O4)[P1.0 3O3.03 OH)0.97]4(H2O)10, with the C, N and H contents constrained by the crystal structure. Raman spectroscopy confirmed the presence of NH4 and C2O4. Relianceite-(K) is monoclinic, Pc, with α = 12.404 (7) Å, b = 9.014 (6), c = 13.260 (8) Å, β = 100.803(10)°, V = 1456 (2) A#93 and Z = 2. The structural unit in the crystal structure of relianceite-(K) (R1 = 0.0540 for 3751 Io > 2σI reflections) is a (V4+O)2(C2O4)(PO3OH)4 chain in which VO6 octahedra are bridged by an oxalate group to form [V2C2O12] dimers, PO3OH tetrahedra form a double bridge between the VO6 octahedra of the dimers, and additional PO3OH tetrahedra decorate the chain. Topologically, this is the same chain found in the structure of davidbrownite-(NH4). The MgO(H2O)5 octahedron can be considered a distant decoration on the chain. The chains are linked to each other through an extensive system of K/NH4-O bonds and hydrogen bonds.